Response modality-dependent abstract choice representations for vibrotactile comparisons

Previous electrophysiological studies in monkeys and humans suggest that premotor regions are the primary loci for the encoding of perceptual choices during vibrotactile comparisons. However, these studies employed paradigms wherein choices were inextricably linked with the physical properties of the stimuli and action selection. It raises the question what brain regions represent choices at a more abstract level, independent of the sensorimotor components of the task. To address this question, we used fMRI-MVPA and a variant of the vibrotactile frequency discrimination task which enabled the isolation of choice-related signals from those related to stimulus properties and selection of the manual decision reports. We identified the left, contralateral dorsal premotor cortex (PMd) and intraparietal sulcus (IPS) as carrying information about abstract choices. Notably, our previous work using an oculomotor variant of the task also reported abstract choice representation in intraparietal and premotor regions. However, the informative premotor cluster was centered in the frontal eye fields rather than in the PMd, providing empirical support for a response effector-dependent organization of abstract choice representation in the context of vibrotactile comparisons. Considering our results together with findings from recent studies in animals, we speculate that the premotor region likely serves as a temporary storage site for information necessary for the specification of concrete manual movements, while the IPS might be more directly involved in the computation of choice.